At present one of the most critical problems in ophthalmological practice is how to correct vision after cataract extraction.
There exist a number of methods for such correction, e.g., spectacles or contact lenses. However, sight correction with the aid of spactacles fails to restore patient's normal visual acuity, while correction with the help of contact lenses is not tolerated well by all patients, especially by aged persons (about 80 to 85 percent) when cataract is most commonly encountered.
That is why ophthalmologists throughout the world have sought for other ways to solve this problem. Another solution of the aforesaid problem is intraocular correction, i.e., implantation of a prosthetic lens.
There are known a variety of constructions of intraocular lenses, a majority of which are for implantation in the anterior eye chamber and for securing to the iris or in the crystalline capsule, where the lens supporting elements are fixed by a suture. Such intraocular lenses are obviously far from meeting all requirements indispensable for full sight correction.
The most successful is an intraocular lens adapted for intracapsular implantation. An eye with an intracapsularly implanted intraocular lens differ in nothing from a normal phakial eye. The crystalline capsule isolates the intraocular lens from the surrounding tissues, thus absolutely precluding its dislocation, while close mutual arrangement of the intraocular lens centre and the centre of a natural crystalline lens helps attain binocular vision in the case of uni- or bilateral aphakia.
However, for successful and more complete sight correct by virtue of intracapsular implantation, use should be made of intraocular lenses based upon a novel principal of intraocular lens fixation in human's eye.
Known in the art is an intraocular lens (cf. USSR Inventor's Certificate No. 563,174, Int.Cl. A 61 F 9/00) having a securing and a supporting element. Both of the elements are substantially identical and are shaped as loop-shaped legs made of a rigid material and fastened on the lens lateral surface, the only difference being in that the securing element has two projections for the suture material to guide and hold. Such a lens is adapted for being implanted in the crystalline capsule.
However, implantation of such an intraocular lens involves a long operative wound commensurable with the overall dimensions of the lens, the supporting elements inclusive. Moreover, the necessity of stitching the eyelets of the securing elements to the lips of the incision in the iris sophisticates the implantation technique of said intraocular lens.
There is also known an intraocular lens (cf., e.g., U.S. Pat. No. 4,316,292, Int.Cl. A 61 F 1/16, issued on Feb. 23, 1982), comprising an optical lens provided with supporting and fastening elements which are fixed to the lens on the diametrically opposite sides thereof, the fastening element being essentially a radially displaceable loop-shaped lug from an elastic material.
The implanting of an intraocular lens in the crystalline capsule of a patient is carried out as follows. After an extracapsular cataract extraction a special calibrated spatula is inserted into the empty crystalline capsule and the distance from the equator to the centre of the crystalline capsule is measured.
Then the supporting element of the intraocular lens made as a loop-shaped lug is either bent out or bent in so as to obtain a distance to the lens centre, corresponding to the distance from the crystalline capsule to the centre of the pupil.
After matching the required parameter of the intraocular lens, the latter is introduced into the crystalline capsule, and the fastening element is stitched up to the basal iridotomy.
However, the aforediscussed implantation of the intraocular lens mentioned above requires a large operative incision, additional devices in the form of a calibrated spatula, and a very high lens adjusting accuracy with the respect to the eye optic axis and, first and foremost, such implantation involves fixing the fastening element in the eye by stitching, which is a very complicated task from technical viewpoint.
Another intraocular lens is also known to comprise an optic lens and radially arranged supporting elements made as rods with rounded-off ends (cf., e.g., U.S. Pat. No. 4,159,546, Int.Cl. A 61 F 1/16; A 61 F 1/24 issued on July 3, 1979).
The aforediscussed intraocular lens is implanted in the posterior eye chamber through the dilated pupil and an incision made in the anterior portion of the crystalline capsule by compressing the supporting element during the implantation procedure and by resting against the ciliary body, followed by fitting the entire lens in a ture position within the posterior chamber.
Such a construction of the intraocular lens requires very high skill on the part of the ophthalmosurgeon for its implantation, since the surgeon must select the efforts to be applied during the implantation at a high degree of accuracy so as to introduce the lens proper into the posterior chamber and to compress the supporting element. Even minutest inaccuracy comitted during the implantation procedure might inflict damage to the patient's eye components.
Another disadvantage of the construction of said intraocular lens consists in that its resting upon the posterior chamber equator occurs substantially at one point on each of the supporting elements, which brings about inevitable vibration of the lens and hence an indistinct image, on the ocular retina, of a visually percepted object while in motion.